Armour reports that the proliferation of portable electronic devices--laptop computers, cell phones, Blackberrys, etc.--has made online porn more common in the workplace. And it has made it more difficult for employers to manage the problem.

About 65 percent of American employers use software to block inappropriate Web sites in the workplace. But portable devices, even ones owned by companies, can help get around such blocks. And employers are concerned about facing lawsuits from workers who say they are offended by the presence of porn at work.

The federal Equal Employment Opportunity Commission has brought several lawsuits against businesses on behalf of workers who said they felt harassed at work because of online porn. One of the best known cases involved First Mutual, a mortgage company in Cherry Hill, New Jersey. Another involved Sierra Aluminum.

On the other side of the legal spectrum is James Pacenza, a former IBM employee. Pacenza sued the company after being fired for visiting an adult chat group while at work. Pacenza, a Vietnam veteran, claimed his firing was discriminatory because he visited the site in order to reduce symptoms from post-traumatic stress disorder (PTSD).

USA Today reports that the problem of porn in the workplace is not likely to go away soon:

Researchers and psychologists who study Internet users' behavior say those who view online porn at work are doing so because they get a rush out of taking risks, engage in self-delusional beliefs that they won't get caught and, in some cases, suffer from addictive behaviors.

The rising use of mobile devices such as video phones could exacerbate the problem, they say.

"This dilemma is going to get much worse, given the capacity of handheld, electronic devices to download porn," says Carleton Kendrick, a psychotherapist in Millis, Mass. "That will eliminate an employer's opportunity to check which workers have been going to porn sites on company computers."